An Application Of Nonlinear Robustness Control Theory In Missile Guidance System

Missile guidance law is one of technical barriers in homing missile's system. Since its inception as an empirical guidance law in forties, proportional navigation(PN) has attracted a considerable amount of interest in the missile guidance literature. Although PN is simple to implement and is also known to be an optimal algorithm for a nonmaneuvering target ,its performance is degrade with target maneuvering and it may be ineffective for some orientations between missile and target. The PN-variant guidance algorithms such as OGL and APN require information about target acceleration, but it is difficult to obtain the information without time delay.Most of the above guidance law are designed with the assumption that the response of the control system is ideal or a lower pass filter .In an actual situation, due to flight conditions and unexpected environments, we cannot expect the ideal performance of the control system. Since the guidance system is designed without addressing this situation, the discrepancy between ideal the control system and actual one can lead to the unsatisfactory performance. Furthermore, most of them is considered only 2-dimensional pursuit situations.Firstly, in this paper, four mathematical models of guidance system are described According to flight dynamics and theory mechanics, missile-target relative kinematics equations considering control loop as one or two order dynamic characteristic are derived in two-dimensional or three-dimensional pursuit situations. The mathematical models includes properties of guidance loop and control loop.Secondly, four novel nonlinear missile guidance laws intercepting maneuver target are proposed for homing missile system. To improve guidance law performance, the simultaneous design of the guidance and control loop, i.e., the integrated missile guidance and control system is formulated by a nonlinear state equation. Based on nonlinear H_∞control theory, four new guidance laws are derived by solving the associated Hamilton-Jacobi Differential Partial Inequalities(HJPDI) in two-dimensional or three-dimensional pursuit situations. Under this new approach, missile control loop dynamics is carefully thought out by the integrated missile guidance and control system and full nonlinear motions are considered without any linearization. These guidance laws do not require the information of target acceleration .Thirdly, the effectiveness and disturbance attenuation level of the new guidance...